The powder booth is well known, and one form of it is described in U.S. Pat. No. 4,723,505. The powder booth has a chamber through which an object to be finished with powder is conveyed. Electrostatic guns fire powder into the atmosphere surrounding the object to be finished, and much of the powder adheres to that object. The remainder of the powder is conveyed by airflow and gravity through the powder booth to a collector. Collectors generally have a filter medium through which the air from the powder booth is drawn, the powder being arrested by the medium. Reverse pulses are from time to time introduced into the reverse side of the medium to knock the powder off the medium, thereby preventing its being clogged. The thus filtered air is then directed through a final filter and into the plant atmosphere. The final filter is provided to assure the cleanliness of the air that is introduced into the plant.
In the powder booth of U.S. Pat. No. 4,723,505, the powder collector consists of a housing that is mounted on castered wheels so that it can be rolled into and out of position adjacent the powder booth, thereby permitting the quick changeover from one color powder to another. The housing has opposed walls with opposed openings in the walls. Extending across the housing is a triangular tower structure formed of three triangularly-spaced rods, the rods being cantilevered from one end of the housing adjacent the air outlet opening. The free end of the tower has a plate and a bolt projecting from the plate, the plate and bolt being located adjacent the opposite opening. A hollow cylindrical cartridge is mounted in the collector adjacent each opening by sliding it over the tower structure. A plate is bolted onto the projecting nut with the bolt tightening the plate against the cartridge and against the wall of the housing. Gaskets are provided at the ends of the cartridge, and a gasket between the plate and the housing wall is provided in order to seal the cartridge within the collector.
The structure described normally provides a satisfactory seal. However, when a collector is transported from the factory to the finisher, tightened bolts become loosened and leakage can occur. Further, if the housing, which is formed of sheet metal, is manufactured slightly out of true so that the opposed walls are not precisely parallel to one another, the clamping of gaskets is not uniform and leakage can occur.
The consequence of leakage is that the powder that leaks past the cartridge flows to the final filter and rapidly builds up on the final filter. When the final filter plugs up due to the flow of excess powder onto it, air ceases to flow from the spray chamber through the collector and the recycle system totally breaks down.
If leakage occurs, it normally requires a mechanic to make the adjustments necessary to stop the leakage.